The present invention relates to the control of missiles in flight.
It is generally accepted that aerodynamic control surfaces, both fixed and moveable, are the most effective means for controlling missile flight within the earth's atmosphere and most missiles make use of them. Although they produce additional drag, their effectiveness in terms of missile weight, turning moment and actuating power consumption is difficult to surpass with any other form of control.
In a surface-to-air missile hitherto proposed, aerodynamic control surfaces have been provided on a rotatable nose portion to bring the nose portion to a required roll attitude and to apply a lateral thrust on the nose portion to steer the missile on to a corrected flight path. This form of control is usually referred to as a “twist and steer” control. Such flight control has also been used in a modified form where the nose portion continues to rotate and the lateral thrust produced by the aerodynamic control surfaces on it made effective at the required roll attitude by braking the nose portion momentarily when in the required roll attitude. The main body portion of the missile has also been provided with control surfaces which cause the body to rotate during flight to provide directional stability. Both forms of “twist and steer” control have been found to be successful for missile guidance in the earth's atmosphere and can be provided at low cost.
In a surface-to-air missile hitherto proposed the aerodynamic control surfaces have comprised a pair of aileron control surfaces and pair of elevator control surfaces which have been effective at low altitude for rotating the nose portion at the required rotational speed and for applying the required lateral steering force on the missile. The reaction forces available at high altitude may however not be found to be sufficient to generate a high enough roll torque to spin the nose portion at a satisfactorily high rotational speed. Furthermore the elevator surfaces which should of course not be so large as to impede launch of the missile may be found to be not large enough to generate sufficient lateral steering force at high altitudes.